66 C. J. CONNOLLY. 



room, so that no light other than that passing through slit of the 

 spectroscope could enter the jar. As the light band of 30 wave- 

 lengths is quite narrow in the red end of the spectrum, the narrow 

 side of the jar faced the light. Four fishes about 5 cm. long were 

 used in each test. The water was renewed by siphoning and kept 

 at room temperature. Each test ran day and night from Monday 

 to Saturday, when fish were examined. 



In the first test, in which the fishes were exposed to the blue 

 light waves between 470 and 500^ in length, the pronounced blue 

 color observed in specimens subjected to prolonged stimulus of 

 blue background as noted above, was absent, the specimens not 

 differing in any noticeable degree from some normal fish. The 

 second test (green) was likewise inconclusive. This is the most 

 difficult change to verify, for in light adapted fish, a green tint is 

 always present. The third test, that of yellow 560 to 590^ 

 gave a decided response, all specimens becoming yellow. It like- 

 wise gave a basis for judging the preceding tests. For if in- 

 tensity alone is a factor in the color changes, since it was equal in 

 all the tests, the specimens in the first two should show the same 

 yellow color as in the third. The experiment was repeated with 

 the same fish after they had again assumed the pale tint by being 

 placed on a white background and the response to yellow occurred 

 again in about 36 hours. Repetition, as observed by Mast and 

 others, increases the rapidity of the response. The fourth tests, 

 that of red which included wave-lengths 610 to 640^ also called 

 forth a yellow response but less pronounced than in the case of 

 yellow rays. 



It is worthy of note that in all tests with spectral light of equal 

 intensity, the shade was about the same, the melanophores being 

 contracted. From this it may be concluded that light of any 

 color has a stimulating effect like that of white light in causing 

 contraction of the melanophores. It shows clearly that intensity 

 of light plays an important role in the expansion or contraction 

 of the melanophores and thus indirectly affects the colors of fishes 

 by exposing or obscuring other color elements. Nevertheless, the 

 fact that the yellow part of the spectrum caused a decisive change 

 to a yellow tint by expanding the xanthophores or yellow pigment 

 cells, while the intensity remained the same as in other spectral 



